McClure, Joseph M.;
Rossi, Noreen F.;
Chen, Haiping;
O'Leary, Donal S.;
Scislo, Tadeusz J.
Vasopressin is a major vasoconstrictor involved in hindlimb vascular responses to stimulation of adenosine A1 receptors in the nucleus of the solitary tract
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Media type:
E-Article
Title:
Vasopressin is a major vasoconstrictor involved in hindlimb vascular responses to stimulation of adenosine A1 receptors in the nucleus of the solitary tract
Contributor:
McClure, Joseph M.;
Rossi, Noreen F.;
Chen, Haiping;
O'Leary, Donal S.;
Scislo, Tadeusz J.
imprint:
American Physiological Society, 2009
Published in:American Journal of Physiology-Heart and Circulatory Physiology
Description:
<jats:p> Our previous study showed that stimulation of adenosine A<jats:sub>1</jats:sub> receptors located in the nucleus of the solitary tract (NTS) exerts counteracting effects on the iliac vascular bed: activation of the adrenal medulla and β-adrenergic vasodilation versus vasoconstriction mediated by neural and unknown humoral factors. In the present study we investigated the relative contribution of three major potential humoral vasoconstrictors: vasopressin, angiotensin II, and norepinephrine in this response. In urethane-chloralose anesthetized rats we compared the integral changes in iliac vascular conductance evoked by microinjections into the NTS of the selective A<jats:sub>1</jats:sub> receptor agonist N<jats:sup>6</jats:sup>-cyclopentyladenosine (CPA; 330 pmol in 50 nl) in intact (Int) animals and following: V<jats:sub>1</jats:sub> vasopressin receptor blockade (VX), angiotensin II AT<jats:sub>1</jats:sub> receptor blockade (ATX), bilateral adrenalectomy + ganglionic blockade (ADX + GX; which eliminated the potential increases in circulating norepinephrine and epinephrine), ADX + GX + VX and ADX + GX + VX + ATX. In Int animals, stimulation of NTS A<jats:sub>1</jats:sub> adenosine receptors evoked typical variable responses with prevailing pressor and vasoconstrictor effects. VX reversed the responses to depressor ones. ATX did not significantly alter the responses. ADX + GX accentuated pressor and vasoconstrictor responses, whereas ADX + GX + VX and ADX + GX + VX + ATX virtually abolished the responses. Stimulation of NTS A<jats:sub>1</jats:sub> adenosine receptors increased circulating vasopressin over fourfold (26.4 ± 10.4 vs. 117.0 ± 19 pg/ml). These data strongly suggest that vasopressin is a major vasoconstrictor factor opposing β-adrenergic vasodilation in iliac vascular responses triggered by stimulation of NTS A<jats:sub>1</jats:sub> adenosine receptors, whereas angiotensin II and norepinephrine do not contribute significantly to the vasoconstrictor responses. </jats:p>